1. Field of the Invention
The present invention relates to a seal for a printhead and the process for producing the seal. More particularly, the invention relates to a removable seal molded to the face of a printhead for sealing the nozzles of the printhead during shipping and handling.
2. Description of Related Art
Thermal ink jet printing systems use thermal energy to produce a vapor bubble in an ink filled channel in a printhead that expels a droplet of ink onto a recording medium, such as paper. The thermal energy is selectively produced by resistors located in capillary-filled ink channels in the printhead near channel terminating nozzles or orifices in the face of the printhead to momentarily vaporize the ink and form bubbles on demand. Each temporary bubble expels an ink droplet and propels it towards a recording medium. The printing system may be incorporated in either a carriage-type printer or a pagewidth type printer. The carriage-type printer generally has a relatively small printhead containing the ink channels and nozzles. The printhead is usually sealingly attached to an ink manifold or to a cartridge assembly and is reciprocated to print one swath of information at a time on a stationarily held recording medium, such as paper. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath, so that the next printed swath will be contiguous therewith. The procedure is repeated until the entire page is printed. In contrast, the pagewidth printer has a stationary printhead having a length equal to or greater than the width of the paper. The paper is continuously moved past the pagewidth printhead in a direction normal to the printhead length and at a constant speed during the printing process.
Ink jet printing systems often experience several problems which adversely affect the quality and performance of printing. Among these problems are 1) evaporation of the volatile ink ingredients, including water; 2) clogging of the printhead nozzles caused by ink drying therein due to non-use for a period of time; 3) adherence of dust to the nozzle-containing face of the printhead due to the moisture of fluid ink around the nozzle; 4) leakage of ink from the nozzles; and 5) bubbles and dust taken into the printhead nozzles.
Shipping and handling prior to installation of a printhead often cause or at least aggravate the above-mentioned problems. A printhead will be jostled and tilted during shipment and installation, often causing ink to leak from the nozzles into the packaging thus wasting ink and resulting in additional time and effort in cleaning the printhead. Further, the nozzles can become clogged with dry ink or debris, and the ink channels can dry up and clog between the time the printhead is packaged for shipping and ultimately installed in a printer.
Therefore, manufacturers of printheads have attempted several techniques to seal the face of a printhead during shipping and handling. One such technique merely consists of applying tape or Mylar to the face of the printhead. However, these materials do not adhere well to the face of the printhead due to irregularities in the surface of the printhead die. Further, tape can leave adhesive residue on the face of the printhead which will later interfere with the printing operation. Another technique involves adhering tape onto the face of the printhead and then pressing a piece of plastic foam onto the tape. However, the foam cover requires additional space, cost and packaging. Also, the face of a thermal ink jet printhead may be uneven or irregular due to tolerances of the channel plate, heater plate, manifold and heat sink. The above materials do not easily accommodate such unevenness and therefore may leave gaps between the face of the printhead and the seal, resulting in leakage.
Thus, there is a need to provide an effective, yet easily removable, seal on the face of a printhead which is easy to manufacture and cost effective.